Prophylactic Risedronate for Patients With Peripheral Lung Tumors Treated With SBRT

2.1 Primary Objective(s) The primary objective is to assess the percent change in bone mean cortical thickness within regions of bone receiving 30 Gy or more at 3 months after SBRT. The % change in mean cortical thickness will be compared between patients who received risedronate and those who received placebo. 2.2 Secondary Objective(s) In addition to the primary objective, the investigators will further analyze the remaining routine follow-up chest CT scans, for mean cortical thickness change in regions of bone that received 0 - 10 Gy, \>10 - 20 Gy, \> 20 - 30 Gy, \> 30 - 40 Gy, and \> 40 Gy at all time points including 3 months, 6 months, 9 months, and 12 months. These scans are standard of care and would be performed regardless of inclusion on this trial. This will allow us to determine the potential persistence of effects from SBRT and bisphosphonate use. The investigators will assess and compare the incidence and grade (per modified CTCAE v.5) of radiation induced chest wall pain within the radiation treatment portal (within the 50% isodose line) at time of each routine follow up visit (3 months, 6 months, 9 months, and 12 months post SBRT). The purpose of utilizing a placebo and double-blind design is that chest wall pain is a subjective finding. Furthermore, it is unclear if chest wall pain from radiation is directly due to bone damage, nerve damage, muscle irritation, or a combination of all of these factors. The use of placebo will help us reduce the potential for bias in pain assessment. The investigators will assess and compare the incidence of rib and vertebral fractures (as noted on CT imaging) that occur within 12 months of irradiation and are within the radiation treatment field. The radiation treatment field will be defined as within the 50% isodose line. The urine concentration of an osteoclast-specific biomarker, urinary N-telopeptide (NTX) indicating osteoclast activity will be assessed prior to SBRT and at each routine follow up visit (at 3 months, 6 months, 9 months, and 12 months post SBRT).